1. Field
One or more exemplary embodiments relate to a golf ball having a surface divided to arrange dimples, in which a surface of a sphere is divided not by great circles GCs but by triangular concave sectors and the dimples are arranged in the divided surfaces so that a spherical surface, that is, an overall concave surface, is increased to more easily facilitate lift, thereby increasing a flight distance.
2. Description of the Related Art
Concave surfaces including dimples in a surface of a golf ball are directly involved in flight in terms of aerodynamics and greatly affect flight performance of the golf ball.
A golf ball being hit by a golf club generates backspin according to a loft angle of the golf club and simultaneously flies forward due to strong repulsive elasticity generated from a core of the golf ball. The golf ball has a flight trajectory that differs according to various formation specifications of the golf ball.
Even when initial trajectories are similar to each other, the shape of a trajectory, a peak of a trajectory, a flight duration, etc. may considerably vary according to the type and shape of dimples and an arrangement of the dimples. Also, even when an identical player hits a golf ball using the same golf club, flight characteristics appear to be different according to a repulsive elasticity capability and rigidness of a golf ball and a difference in spin performance of the golf ball. Particularly, flight duration, height of a peak, straight flight feature, wind effect, etc. may vary greatly according to the shape, size, number, area ratio, depth, arrangement method of dimples, etc.
Among them, an area ratio occupied by dimples is an important factor for the flight characteristics as well as the size of a dimple. As the area ratio increases, lift may be easily increased.
In general, circular dimples are widely used for dimple arrangement. For a relatively small circular dimple, lift may be difficult to achieve, but wind effect may be less, thereby enabling stable flight. In contrast, for a relatively large circular dimple, lift may be easily achieved but wind effect is greater and thus flight stability is deteriorated. Accordingly, the golf ball flies in an unintended direction, rather than toward a desired destination. Also, in the case of a large dimple, when putting, there may be a difference between when a surface of a putter contacts a land surface where no dimple is formed and when the surface of a putter directly contacts a surface of a dimple and thus a directional consistency may not be guaranteed. In general, a golf ball having a relatively large sized dimples, so that the number of dimples over an entire surface of the golf ball are about 252˜312 circular dimples, may have a trajectory that is too high. Accordingly, the golf ball may be greatly affected by the wind and thus a flight distance may become irregular and directivity may be deteriorated. In particular, the error may become severe when short distance putting. A golf ball having many small dimples and less large dimples, that is, about 372˜432 dimples, may have a relatively low trajectory and may be less affected by the wind compared to the above-described golf ball having many relatively large dimples. However, it may be seen that a flight distance of a golf ball hit by a golf club with a fast head speed relatively increases. Accordingly, when the head speed is slow, particularly in the case of a golf ball having a soft touch, it may be difficult to obtain a desired flight distance.
Accordingly, many manufacturers have developed golf balls which may increase a flight distance by increasing an area ratio of dimples to help achieve lift which increases a flight duration. The following are examples of golf balls invented as a result of the above.
U.S. Pat. No. 5,494,631 discloses that a dimple area ratio is increased to its maximum by arranging dimples on the equator of a golf ball. Although a dimple area ratio may be increased, since a precise process to remove resin burr left in the dimples located on the equator is needed, considerable time is needed for a grinding process.
U.S. Pat. No. 6,709,349 discloses that a dimple area ratio is increased by arranging dimples on the equator of a golf ball and setting several dimples in a group, and a mold parting line is formed above a dimple group and then under a next dimple group so that the mold parting line is alternately formed on an upper mold and a lower mold. When a dimple is larger than a certain size, the dimple may be damaged during post-processing.
U.S. Pat. No. 7,618,333 discloses that dimples located over a mold parting line form a so-called seamless mold parting line. The mold parting line having a zigzag amplitude of 0.02 inches or less causes dimples to tightly contact each other above and under the mold parting line without spaces therebetween. Accordingly, a dimple area ratio is higher than a general mold parting line formed of a straight line and the dimples may be regularly arranged. In this case, however, buffing to prevent damage to the dimples may be difficult.